Larry Eiselstein

The factors leading up to the large explosion that occurred in an ammonium nitrate neutralizer in Iowa in 1994 will be discussed. Ammonium nitrate (in the form of 83 wt.% solution in water) was made in a neutralizer tank by reacting nitric acid with ammonia. At the time of the accident, the neutralizer had been shut down but the contents were kept hot by steam injected through the nitric acid sparger. Several operational factors combined to cause the explosion: the ammonium nitrate was… Show more

The factors leading up to the large explosion that occurred in an ammonium nitrate neutralizer in Iowa in 1994 will be discussed. Ammonium nitrate (in the form of 83 wt.% solution in water) was made in a neutralizer tank by reacting nitric acid with ammonia. At the time of the accident, the neutralizer had been shut down but the contents were kept hot by steam injected through the nitric acid sparger. Several operational factors combined to cause the explosion: the ammonium nitrate was acidified when the nitric acid line was purged into the neutralizer; the neutralizer contents were not being circulated to maintain homogeneity; the neutralizer had been contaminated with chlorides; the prolonged steam heating raised the neutralizer temperature; and the steam bubbles facilitated runaway decomposition. Show less

Shape memory and superelastic alloys are alloys that exhibit thermally recoverable strain (shape memory effect), pseudoelastic (superelastic behavior), or both. This chapter discusses what is known about the corrosion behavior of such alloys. Most of the information of such materials is focused on nitinol since this material has extensive use in biomedical applications. The corrosion data on other shape memory or superelastic materials will be discussed when available. There are also ceramic… Show more

Shape memory and superelastic alloys are alloys that exhibit thermally recoverable strain (shape memory effect), pseudoelastic (superelastic behavior), or both. This chapter discusses what is known about the corrosion behavior of such alloys. Most of the information of such materials is focused on nitinol since this material has extensive use in biomedical applications. The corrosion data on other shape memory or superelastic materials will be discussed when available. There are also ceramic and polymer materials that exhibit shape memory; however, they are notdiscussed in this chapter. Show less

This handbook chapter describes a general failure analysis methodology with specific applications and examples pertaining to corrosion failures.

Crevice corrosion is a form of localized attack that occurs within occluded regions or crevices of metallic components. The attack is caused by a change in the environment of the crevice relative to the bulk solution. Usually, the term crevice corrosion is limited to describing the attack in normally passive metals and alloys (e.g., stainless steels); however, in the broader sense, the corrosion of nonpassive metals and alloys (e.g., carbon steel) by differential aeration may also be regarded… Show more

Crevice corrosion is a form of localized attack that occurs within occluded regions or crevices of metallic components. The attack is caused by a change in the environment of the crevice relative to the bulk solution. Usually, the term crevice corrosion is limited to describing the attack in normally passive metals and alloys (e.g., stainless steels); however, in the broader sense, the corrosion of nonpassive metals and alloys (e.g., carbon steel) by differential aeration may also be regarded as a form of crevice corrosion. Crevices occur in many engineered structures; consequently, crevice
corrosion is a common form of corrosion in most, if not all, industries. In this chapter, the emphasis is on the crevice corrosion of passive metals and alloys in aerated chloride environments
since this is one of the most common types of crevice corrosion. The mechanisms of crevice corrosion are discussed, together with the effects of the many variables that affect it. Modeling and testing for resistance to crevice corrosion are discussed, as are practical design aspects and methods to minimize attack. Finally, some industry-specific examples of crevice corrosion are provided. Show less

ASTM F 2129 test method nor the FDA provides any guidance as to what constitutes an acceptance criterion for the corrosion resistance of implantable medical devices. Neither provide any guidance on how many samples to test or how to handle censored data, i.e. datasets where there are only a few tests that breakdown. The development of both a statistically valid acceptance criterion for corrosion resistance and a method of evaluation would be of significant benefit to the medical device… Show more

ASTM F 2129 test method nor the FDA provides any guidance as to what constitutes an acceptance criterion for the corrosion resistance of implantable medical devices. Neither provide any guidance on how many samples to test or how to handle censored data, i.e. datasets where there are only a few tests that breakdown. The development of both a statistically valid acceptance criterion for corrosion resistance and a method of evaluation would be of significant benefit to the medical device community. This study of 420 nitinol cyclic polarization tests, which builds on previous research that was presented at SMST 2007, investigates the effect of long-term exposure to simulated in vivo environments with differing degrees of aeration. This was accomplished by pre-exposing electropolished (EP) nitinol to phosphate buffered saline (PBS) at 37 ?C that had been sparged with either ultra high purity nitrogen or laboratory air. Immersion times ranged from 1 h up to 30 days. A total of 290 EP samples were tested in order to obtain a reasonable number of samples with breakdown, i.e. pitted. In addition, a total of 130 mechanical polished (MP) samples were also analyzed. This data allow us to test our statistical model that was presented at SMST 2007. This model takes into account the probability of breakdown per unit of exposed surface area and, if breakdown occurs, predicts the probability that Eb2Er is greater than some threshold value. Aerated PBS environments were found to have a large influence on the margin of safety against pitting in vivo. Statistical methods for treating highly right censored pitting data are presented. Show less